Electromagnetic valve

ABSTRACT

The invention relates to an electromagnetic valve, with a valve tappet guided in a valve housing that exhibits a valve-closing element, with a valve-seat holding element facing the valve-closing element, which forms an independent subassembly together with the valve housing, as well as with an armature that activates the valve tappet and can be excited by means of a valve coil arranged on the valve housing. The armature is designed as a cold extrusion pressed part and the valve housing is designed as a deep drawn part or cold extrusion pressed part.

TECHNICAL FIELD

The present invention relates to an electromagnetic valve.

BACKGROUND OF THE INVENTION

These types of conventional valves, known in the prior art, forregulating the flow of fluids in slip-controlled hydraulic brake systemsare being used in many practical applications.

DE 198 088 26 A1 already disclosed an electromagnetic valve for aslip-controlled hydraulic brake system that is open in its startingposition. It has a cartridge-type valve housing which preferably isexecuted as a turned part from machining steel and wedged into ablock-shaped valve-holding element. The valve plate forming the valveseat also preferably is made from a relatively solid turned part ofmachining steel, which is held at the lower end of the valve housing bymeans of a wedge. The valve tappet acting together with the valve seatis guided within the valve housing and is a solid shaft part consistingof a solid cylinder, which is supported on one face of the armature inconnection with an adjusting bushing, with the armature being guidedalong the valve housing within the area of the valve sleeve. In order tokeep the valve tappet lifted away from the valve seat in the startingposition of the electromagnetic valve, a so-called pull-back spring isprovided co-axially to the valve tappet, and it pushes the valve tappetwith the adjusting bushing in the direction of the armature with one endof its spring.

Electromagnetic valves that are closed in their starting position alsohave been disclosed, for example in DE 19 72 7654 A1. In contrast to theabove-described valve that is open in its starting position, the valvetappet, which is cut from a solid, in the valve closed in its startingposition is an essentially independent assembly with the armature, andthis subassembly is oriented towards the valve seat by means of apressure spring supported on the magnetic core, keeping this closed inthe above-mentioned starting position of the electromagnetic valve.

A disadvantage of the above-mentioned electromagnetic valves is therelatively extensive manufacturing process required for producing theindividual units of the valve as well as the production and applicationof a functioning overall assembly in a valve holding element.

Thus, it is the object of the present invention to improve the design ofan electromagnetic valve that is open or closed in its starting positionin such a way that the manufacturing process can be significantlyreduced while still ensuring the functional safety and maintaining arelatively simple, miniaturized design.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1a to 1 e show suitable embodiments of an electromagnetic valvethat is open in its starting position.

FIGS. 2a to 2 d show various design variants of an electromagnetic valvethat is closed in its starting position.

FIG. 3 provides an embodiment of the electromagnetic valves shown inFIGS. 1a to 1 e.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

On the basis of FIG. 1a, the basic design of the electromagnetic valvethat is open in its starting position will be described. Thecross-section of the electromagnetic valve shows a bush-shaped valvehousing 3 that has guide surfaces 3 a, 3 b on both ends to hold adome-shaped valve sleeve 1 and, on the other end, a pot-shapedvalve-seat holding element 7. Thus, the valve housing 3 forms a suitablecentral element for the above-mentioned parts, which simultaneouslyassumes the function of the magnetic core 25. In order to achievelow-cost manufacturing of the above-mentioned parts, the valve housing 3is designed as a cold extrusion pressed part and the valve sleeve 1 aswell as the pot-shaped valve-seat holding element 7 are designed as deepdrawn parts, with the valve-seat holding element 7 in the pot-shapedbottom providing, by means of a stamping process, the two valve-seatsurfaces for a return valve 10 and the valve closing element 9 mountedon the valve tappet 4. Another design, meaningful as regardsmanufacturing and function, arises when the valve tappet 4 is designedas a thin-walled sleeve part, which can be produced at low cost andprecisely as a rotary kneaded part or possibly also as a deep drawnpart. The simple contours of the thin-walled design of the valve tappet4 allow a particularly advantageous placement of the pull-back spring 8,which is held concentrically on valve tappet 4, so that one end of itswinding is supported on a funnel-shaped extension of the lifter shaftand its other end is supported on the bottom of the pot-shapedvalve-seat holding element 7. In the design shown in the drawing, theactual valve closing element 9 is formed by a steel ball that isencompassed in a tong-like manner at the end of the valve tappet 4. Inaddition, on the side facing away from the valve closing element 9 atthe bottom of the pot-shaped valve-seat holding element 7, there is thealready mentioned return valve 10—also designed as a steel ball —whichis fixed in its position at bypass opening 12 that exhibits the secondvalve seat at the bottom of the pot by means of a filter pot 11 pushedover the valve-seat holding element 7. Adjusting pin 2 protrudes fromwithin the valve tappet 4 in the direction of the armature 13. Theadjusting pin has a polygonal profile which, according to sectional viewA—A, has a triangular profile section and can be shifted within thelifter pipe in order to adjust the residual air gap of the armature,forming a press fit with the tappet pipe.

In addition, it needs to be pointed out that after the adjusting pin 2is completely adjusted all above-mentioned parts can be additionallyfixed in their positions in the valve tappet 4 by means of appropriatenon-positive and/or positive fits.

Another way of contributing to low manufacturing costs for theelectromagnetic valve is that the armature 13, also made from acold-extrusion pressed part, which, according to the figure, extends inthe valve sleeve 1 above the valve housing 3 acting as magnetic core 25.The armature also can be made from a polygonal profile. Preferably thearmature can be adjusted in the valve sleeve 1 independently of theposition of the-valve tappet 4. Thus, the armature 13 and valve tappet 4form independent parts which, although they are connected as axial forcetransmission elements, are effective independently of one another in aradial direction. Since the valve tappet 4 basically is designed like apipe and the adjusting pin 2 as well as, if applicable, the armature 13have polygonal profiles, there is an unchecked pressure compensationwithin the valve tappet 4, which is equipped with a transverse channeland within the valve sleeve 1 into the hollow spaces 15, 16 arranged onboth sides of the valve housing 3. Hence, the electromagnetic valveformed into a cartridge hereby only has, as a means of fastening in theblock-shaped valve support 6, a relatively thick-walled section of valvehousing 3 in the vicinity of the wedge 17 designed as a shoulder 5, atwhich, due to the axial wedging force-acting on the valve support 6, aprimarily non-positive connection of the electromagnetic valve in thelocation hole 18 of the valve support 6 is obtained. The location hole18 is designed as a graduated bore, with the edge 20 of the pot-shapedvalve-seat holding element 7 being wedged tightly (i.e. providingtightness against fluids) between the shoulder 5 on the valve housing 3and a step 19 in the valve support 6. The prolongation 31 with theguiding surface 3 b on the valve housing 3 extending into the pot-shapedvalve-seat holding element 7 ensures that the valve-seat holding element7 can be safely pre-assembled and handled on the valve housing 3 beforethe corresponding parts in connection with the filter pot 11 and thereturn valve 10 included therein are inserted in the valve support 6.For example, the valve sleeve 1 is not only pushed over a cylindricalprojecting part with the guiding surface 3 a of the valve housing 3, butalso attached permanently by means of a welded joint 19 when theadjustment has been completed. Naturally, alternative methods ofpositive and non-positive fastening can be used instead of the weldedjoint 19. With the exception of the return valve 10 arranged on the sideof the valve, all other above-mentioned parts are arrangedconcentrically with respect to the longitudinal axis of the valve.

In contrast to the embodiment according to FIG. 1 described above,design variants of the electromagnetic valve, including any detailsdifferent from FIG. 1a, will now be described. Whenever certain detailsof the respective valve variants are not described, they correspond tothe embodiment shown in FIG. 1a and can be found in the descriptionabove.

FIG. 1b, contrary to FIG. 1a, shows an electromagnetic valve where aseparate sleeve element 22 having a press fit in the valve-seat holdingelement 7 is pressed into its pot-shaped valve-seat holding element 7.Such sleeve element 22 exhibits a conical sealing surface acting asvalve seat on the face turned towards the valve closing element 9. Forthe purpose of adjusting the residual air gap of the armature, thesleeve element 22 assumes the function of the adjusting pin 2 describedin connection with FIG. 1a, since the pipe-shaped valve tappet 4,contrary to FIG. 1, now abuts directly against the face of the armature13 in FIG. 1b.

In the embodiment of the electromagnetic valve according to FIG. 1c, thesleeve body 22 described for FIG. 1b also is used; however, with thedifference that it is directly inserted by means of a press fit into thevalve housing 3 extending in the direction of the filter bottom, sothat, contrary to the FIGS. 1a and 1 b, the valve-seat holding element 7forms a single component of the valve housing 3.

In close approximation of the embodiment according to FIG. 1b, FIG. 1dshows an electromagnetic valve whose pot-shaped valve-seat holdingelement 7 is provided with a particularly thin, sleeve-shaped section inthe area of the solid sleeve element 22, over which the filter pot 11 isslipped. Both the return valve and the bypass channel 12 associated withthe return valve 10 are skillfully comprised in the filter pot 11. Thevalve-seat holding element 7 is fastened to the valve housing 3 by meansof a radial wedge attached from outside onto the guiding surface of thethin-walled valve-seat holding element 7, which can be recognized as thenose 23 directed into the prolongation 31 in the selected sectionalview.

In a surprisingly simple manner, all of the electromagnetic valves shownup to now can assume the function of a pressure control valve, and thiswill be described below on the basis of FIG. 1e. Due to the fact thatthe pipe-shaped valve tappet 4 contains a cylindrical hollow space ofcorrespondingly generous dimensions, the valve-closing element 9 can bearranged in an axially movable manner instead of the hitherto describedfixed arrangement of the valve-closing element 9. For this purpose, thevalve-closing element 9, taking the form of a plunger, would be insertedfrom above into the hollow space of the valve tappet 4 until its conicalstop shoulder abuts against the tapered end of the tappet and, at thesame time, its closing element protrudes from the open end section ofthe valve tappet 4 and is turned towards, by means of spring pressure,the sleeve element 22 or valve-seat holding element 7. The openingpressure is decisive as regards the function of pressure control valveand is determined by means of a valve spring 24, which is wedged betweenthe valve-closing element 9 and a stop pressed into the valve tappet 4.Thus, in the electromagnetically activated closed position of the valve,the valve-closing element 9 abuts tightly (i.e. providing tightnessagainst fluids) against the valve-seal holding element 7 in a mannerknown in the prior art until the hydraulic pressure below the valve-seatholding element 7 exceeds the pressure applied by the valve spring 24onto the valve-closing element 9, causing the valve-closing element 9 tobe lifted from its valve seat and thereby realizing the function of apressure control valve.

In the following, the essential characteristics of the invention will beexplained explicitly on the basis of an electromagnetic valve that isnormally closed in its starting position (see FIG. 2a) Subsequently,possible variations of the components of the valve will be described onthe basis of FIGS. 2b to 2 d.

Like the electromagnetic valves according to FIGS. 1a to 1 e, theelectromagnetic valve according to FIG. 2a has an armature 13 producedas a cold extrusion pressed part, a magnetic core 25 made from a coldextrusion pressed part, and a pot-shaped valve-seat holding element 7that is attached to the valve housing 3. To the extent that thin-walledsleeve parts are applied, they are also designed, as in the aboveembodiments, as deep drawn parts or, possibly, rotary kneaded parts. Inthis connection, FIG. 2a shows a sleeve-shaped valve housing 3 that isdesigned as a deep drawn part. Its two end sections form guidingsurfaces 3 a, 3 b, which are limited on one side by a magnetic core 25and on the other side by the pot-shaped valve-seat holding element 7.Both parts 25, 7 arranged on the sleeve-shaped valve housing 3preferably are attached permanently by means of a welded joint 19.Within these parts, which were already described above, there is anarmature 13 that has on its windings—as shown in FIG. 1—either pressurecompensation grooves or a cornered profile in order to ensure uncheckedhydraulic pressure compensation in the valve. As already mentioned inconnection with FIG. 1, the armature 13 and magnetic core 25 aredesigned as cold extrusion pressed parts, for which purpose a materialwith the identification code X8Cr17 or alternatively a material with theidentification code X6Cr17 is suitable. The sleeve-shaped valve housing3 preferably is made of austenitic steel according to classification1.43.03. The same material is used for the pot-shaped valve-seat holdingelement 7, with this material also being selected for the previouslymentioned sleeve components of the electromagnetic valves according toFIGS. 1a to 1 e. The electromagnetic valve according to FIG. 2a isattached in the valve support 6 directly on the edge 20 of thepot-shaped valve-seat holding element 7 by means of an outside wedge.The pot of the valve-seat holding element 7, as in all previousembodiments, exhibits at least one radially and axially oriented hole,with the hole arranged in the longitudinal axis of the valve forming theactual valve-seat holding element 7 for the valve-closing element 9 bymeans of a stamping process, whereas the hole penetrating the valve-seatholding element 7 at a right angle thereto as a rule is designed as ahole in order to establish a connection for the pressure medium betweenthe channels in the valve support 6 located below and above thevalve-closing element 9 when the valve is in an open position. A ballwedged into the armature 13 is preferably used as the valve-closingelement 9, and it is pressed onto the valve-seat surface of thevalve-closing element 9 by the effect of a pull-back spring 8 that isarranged between the armature 13 and magnetic core 25. The pot-shapedvalve-seat holding element 7 is sealed in a stepped hole of the valveseat 6 by means of an O-ring 28 arranged between the valve-seat holdingelement 7 and valve support 6. A ring-type filter 29 extends along thevalve-seat holding element 7 up to the O-ring 28, providing additionalholding and/or transportation protection for the O-ring 28 prior toactual assembly in the stepped hole of the valve support 6. Towards theoutside, the electromagnetic valve merely is sealed and fastened in thevalve support 6 by means of a simple outside wedge, whereas the lowerseal created by the O-ring 28 in the valve support 6 prevents a shortcircuit current between the channel flowing into valve support 6 belowthe valve-closing element 9 and the transverse channel located at thelevel of the ring-type filter. The magnetic core 25 is pressed into theopen area of the sleeve-shaped valve housing 3 like a stop and fixed inplace permanently by means of a welded seam after completion of therequired adjusting measures. Due to corresponding projections betweenthe magnetic core 25 and armature 13, which may be arranged either onone or the other of the above-mentioned parts 13, 25, any freezing ofthe armature is prevented. To achieve space-saving holding and guidanceof the pull-back spring, the armature 13 is provided with a longitudinalhole corresponding to the Figure. All parts described are in a coaxialposition.

Based on FIG. 2a, deviating details will be described below; these canbe viewed as alternatives or supplements to FIG. 2a.

FIG. 2b, based on the electromagnetic valve according to FIG. 2a, showsa detail variant of the valve housing 3, whose sleeve-shaped sectionextends up to below the valve-closing element 9 and there holds apot-shaped valve-seat holding element 7 which, contrary to FIG. 2a, isnot connected by welding to the valve housing 3, but instead is merelypressed up to its stop onto an offset step of the valve housing 3. If aknife-shaped prolongation 31 of the valve housing 3 extends from thisarea into the lower channel connection of the valve support 6, it can,if required or desired, cause a metallic sealing, which is shown on theleft side of the sectional view in the representation. In therepresentation shown on the right side of the longitudinal axis of thevalve, the O-ring 28 already described in connection with FIG. 2a isshown as an additional sealing element, which, however, gives rise toadditional costs. An annular part 32 wedged into the valve support 6 isjoined by welding to the valve housing 3 in order to seal off and fastenthe valve.

FIG. 2c shows a two-part embodiment in the form of a flanged connectionof the two parts of the sleeve, with the outer edge 20 of the flangedconnection simultaneously forming the wedging area of theelectromagnetic valve in the valve support 6. All other detailscorrespond to the descriptions given for FIGS. 2a and 2 b.

FIG. 2d shows an electromagnetic valve that is closed in its startingposition. It exhibits an additional function in the form of a so-calledtwo-step valve, for which purpose the valve-closing element 9 arrangedon the armature 13 does not abut directly against the valve-seat holdingelement 7 wedged into the valve support 6, but contacts a secondvalve-seat holding element 7′ that is guided movably within theabove-mentioned valve-seat holding element 7. A valve spring 24 isarranged between both valve-seat holding elements 7, 7′, and it ensuresthat, when the armature 13 is excited electromagnetically, thevalve-seat holding element 7′, which is designed as an intermediate pot,follows the motion of the armature 13, provided that pressurecompensation prevails on both sides of the valve-seat holding element7′, Thus, the inner valve-seat holding element 7′ remains at thevalve-closing element 8 of the armature 13 and, consequently, therelatively small valve-seat opening stays closed due to the ball-shapedvalve-closing element 9. A connection for the pressure medium betweenthe pressure medium channels running vertically and horizontallynecessarily is established through the relatively large cross-section ofthe valve seat, arranged between the two valve-seat holding elements 7,7′, when the armature 13 is in an excited state. When the hydraulicpressure prevailing above the valve-closing element 9 is greater thanthat below the valve-closing element 9, the inner valve-seat holdingelement 7′ is pushed against the outer valve-seat holding element 7 evenwhen the armature 13 is excited electromagnetically; however, only therelatively small valve-seat opening of the inner valve-seat holdingelement 7′ is released by the valve-closing element 9. The outer andinner valve-seat holding elements 7, 7′ are designed as cold extrusionor deep drawn parts, so that in particular relatively small parts, whichcan be produced simply and precisely, are to be inserted in the locationhole of the valve support 6. Like the outer valve-seat holding element7, the inner valve-seat holding element 7′ also should be provided withgenerously dimensioned pressure medium holes 26 and gliding surfaces inthe vicinity of the pot expansion in order to ensure that the innervalve-seat holding element 7 can be guided safely.

Contrary to the valve design according to FIG. 1c, the electromagneticvalve according to FIG. 3 shows a hollow cylindrical valve housing 3that is somewhat shortened in its length. At the lower end a sleeveelement 22, preferably designed as a deep drawn part, is pressed intothe hollow space 16, which, on the one hand, exhibits a valve-seatcontour facing towards the valve-closing element 9 and, on the otherhand, is provided with another valve-seat contour on the opposite endfor the return valve 10. In order to prevent the return valve 10 fromfalling out and to position it firmly in its place, a sleeve part 35 isinserted from below into the pressure medium hole 27 penetrating thesleeve element 22, which, as in the previous example of an embodiment,assumes the function of a defined opening due to the small, selectedcross-section of the opening. Outside its pressed-in length in thesleeve element 22, the sleeve part 35 exhibits a projecting end axiallyand radially respectively, between which the ball-shaped return valve 10is held on the extended area of the sleeve element 22 exhibiting thevalve-seat contour. In the example of the embodiment according to therepresentation, the radial projecting end can be recognized as tongue 36of the sleeve part 35, which is designed as a deep drawn part. Hence,thesleeve part 35 together with the return valve 10 and sleeve element 22forms a pre-assembled unit, which is pressed into the channel-likehollow space 16 as far as necessary for setting the valve stroke. Thebypass opening 12 already described in connection with FIG. 1c nowextends as a longitudinal groove in the area of the press fit along thelateral surface of the sleeve element 22 into the hollow space 16. Thefilter pot 11 is pushed over the end of sleeve part 35 projecting fromthe stepped sleeve element 22, thereby establishing a fixed connectionthat is tight against fluids. Any details of the valve according to FIG.3 not described correspond to the description of the valve according toFIG. 1c or one of its variants according to FIGS. 1a, 1 b, 1 d or 1 e.

What is claimed is:
 1. An electromagnetic valve, comprising: a valvetappet guided in a valve housing that exhibits a valve-closing element,a valve-seat holding element facing the valve-closing element whichforms an independent subassembly together with the valve housing, anarmature that activates the valve tappet and can be excitedelectromagnetically, a valve coil arranged on the valve housing, whereinthe armature is designed as a cold extrusion pressed part and whereinthe valve housing is designed as a deep drawn part or cold extrusionpressed part.
 2. An electromagnetic valve as claimed in claim 1, whereinthe armature is made of a material according to identification codeX8Cr17 or X6Cr17.
 3. An electromagnetic valve as claimed in claim 1,wherein the valve housing has an end section with a guiding surface,onto which the valve-seat holding element is pushed, and wherein thevalve-seat holding element has the form of a pot, whose edge is attachedby means of a wedge to a step of a location hole in a valve support. 4.An electromagnetic valve as claimed in claim 3, wherein the valve-seatholding element is designed as a deep drawn part from a thin-walledmetal coat and that a valve seat limiting a pressure medium hole isarranged on the bottom of its pot by means of a stamping process.
 5. Anelectromagnetic valve as claimed in claim 4, wherein the valve-seatholding element supports a filter pot along its wall, which covers thepressure medium hole made in the valve-seat holding element.
 6. Anelectromagnetic valve as claimed in claim 1, wherein a part of the valvehousing forming a magnetic core is designed as a cold extrusion pressedpart according to material classification X8Cr17 or X6Cr17.
 7. Anelectromagnetic valve as claimed in claim 1, wherein the valve tappet isformed into a thin-walled pipe part from a rotary kneaded part or deepdrawn part, and wherein the valve-closing element is supported on itsend section facing the valve-seat holding element.
 8. An electromagneticvalve as claimed in claim 7, wherein an adjusting pin is pressed intothe end section of the pipe-shaped valve tappet facing the armature, andwherein the end of the adjusting pin projecting from the valve tappet issupported on the armature.
 9. An electromagnetic valve as claimed inclaim 8, wherein a pull-back spring is clamped between the valve tappetand the valve-seat holding element.